This research program will produce investigations of the functional properties within the limited population of identifiable neurons, in the segmental nervous system of the leech, which contain monoamines. Nine ganglionic neurons contain serotonin: the large Retzius cell pair has peripheral projections, while the seven small cells are highly-arborized interneurons. Two peripherally-positioned cells contain dopamine and project into the central ganglia and connectives. We shall measure the central and peripheral release of amines using chromatography and fluorometry. It is of interest to quantify the release of serotonin and dopamine by both intracellular stimulation and activation of pre-synaptic, sensory pathways. Data regarding the annual variations in amine levels and within feeding-starvation cycles will be garnered as well. Functional connections of the amine neurons will be investigated by describing their pre-synaptic excitatory input with electrophysiological techniques. The modulatory effects (output) of stimulated amine neurons and the effects of applied amines upon several organ systems will be investigated. The physiological effects of serotonin and dopamine upon salivary gland cells, jaw motoneurons and muscle fibers, pharyngeal peristalsis, and gut contractility will be investigated in detail with physiological methods. The quantitative effects of amines upon feeding behavior will be examined by the pharmacological-manipulation of serotonin and dopamine levels. Amine effects upon behavioral activation, orientation, bite frequency, and blood meal size will be examined with both elevated and depressed levels of serotonin and dopamine. These experiments could demonstrate the interactions, within a population of biochemically related neurons, which serve to modulate and control cells, in several diverse organ systems, which are integrated to produce a biologically-signigicant behavior.